The present invention relates generally to an improved heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, thermal storage system, air cooler or air heater. More specifically, the present invention relates to a combination or combinations of separate indirect and direct evaporative heat exchange sections or components arranged to achieve improved capacity and performance.
The invention includes the use of a coil type heat exchanger as an indirect heat exchange section. Such indirect heat exchange section can be
combined with a direct heat exchange section, which usually is comprised of a fill section over which an evaporative liquid such as water is transferred, usually in a downwardly flowing operation. Such combined indirect heat exchange section and direct heat exchange section together provide improved performance as an overall heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater.
Part of the improved performance of the indirect heat exchange section comprising a coil type heat exchanger is the capability of the indirect heat exchange section to provide both sensible and latent heat exchange with the evaporative liquid which is streamed or otherwise transported downwardly over and through the indirect heat exchange section. Such indirect heat exchangers are usually comprised of a series of serpentine tube runs with each tube run providing a circuit of a coil. Improved performance of such indirect heat exchangers is achieved by opening the spacing between the generally horizontal tube runs in one or more of the serpentine coil return bends. Such opened spacing in the serpentine coil return bends creates a more efficient cooling zone for the evaporative liquid flowing downwardly over the serpentine coils.
Various combinations of the heat exchange arrangements are possible in accordance with the present invention. Such arrangements could include an arrangement having an indirect heat exchange section with increased vertical spacing in the series of serpentine tube runs formed by increased height return bends. In such an arrangement, an evaporative liquid flows downwardly onto and through the indirect heat exchange section with such evaporative liquid, which is usually water, then exiting the indirect section to be collected in a sump and then pumped upwardly to again be distributed downwardly over the indirect heat exchange section. In this counterflow arrangement, embodiments work more efficiently with generally lower spray flow rates, in the order of 2-4 GPM/sq. ft. In other arrangements presented, the design spray flow rates may be higher.
In another arrangement, a combined heat exchange apparatus is provided with an indirect heat exchange section comprised of serpentine tube runs over which and evaporative liquid is distributed downwardly onto and through the indirect heat exchange section. Such indirect heat exchange section is comprised of serpentine tube runs having an increased spacing between one or more return bends of increased height. Further, a direct heat exchange section comprised of fill can be located in one or more of the areas of increased vertical spacing formed by the return bends of the serpentine coil. In this arrangement, the embodiments work more efficiently with generally lower spray flow rates, in the order of 2-4 GPM/sq. ft. So not only are the embodiments presented within more efficient providing increased heat rejection but they also do it with less energy requirement for the spray water pump. In other arrangements presented, the design spray flow rates may be higher.
Further, it is also part of the present invention to provide a second, intermediate spray water distribution arrangement whereby the evaporative liquid is distributed downwardly over the indirect and, if present, the direct heat exchange sections, at a point below the top of the indirect heat exchange section For this arrangement, there are several different modes of operation which further improve the heat transfer capabilities and customer benefits. In one mode of operation, both the top and intermediate spray sections are active and spray water onto the indirect and direct sections is present. In another mode of operation, the intermediate spray section is not active and the top spray arrangement provides the evaporative liquid to the entire assembly. In yet another mode of operation, the top spray section is not active and the intermediate spray section is active which can provide evaporative cooling for the lower coil section while providing dry sensible cooling for the dry upper coil section. In yet another mode of operation, the top spray section is not active, the intermediate spray section is active, there is selectively no heat transfer from the lower coil section beneath the intermediate spray section allowing the upwardly flowing air to become adiabatically saturated through the direct section if present before transferring sensible heat with the top portion of the coil above the intermediate spray section. This last mode of operation further reduces the amount of water use while providing lower temperature air to provide sensible cooling to the top portion of the coil above the intermediate spray arrangement.
The heat exchanger apparatus or fluid cooler of the present invention could be operated wherein both air and an evaporative liquid such as water are drawn or supplied across both the indirect and direct heat exchange section if present. It may be desirable to operate the heat exchanger without a supply of the evaporative liquid, wherein air only would be drawn across the indirect heat exchange section and across a direct section if present. It is also possible to operate a combined heat exchanger in accordance with the present invention wherein only evaporative liquid would be supplied across or downwardly through the indirect heat exchange section and the direct heat exchange section if present, and wherein air would not be drawn by typical means such as a fan.
In the operation of an indirect heat exchange section, a fluid stream passing through the serpentine coils is cooled, heated, condensed, or evaporated in either or both a sensible heat exchange operation and a latent heat exchange operation by passing an evaporative liquid such as water together with air over the serpentine coils of the indirect heat exchange section. Such combined heat exchange results in a more efficient operation of the indirect heat exchange section, as does the presence of the increased spacing formed in one or more of the return bends of the serpentine tube runs of the indirect heat exchange section. Further efficiency in operation can also be achieved by the provision of a second or intermediate spray distribution system for providing evaporative liquid to flow downwardly onto and through the serpentine coils of the indirect heat exchange section. The evaporative liquid, which again is usually water, which passes generally downwardly through the indirect heat exchange section and generally downwardly through the direct heat exchange section which is typically a fill assembly, if such a direct heat exchange section is provided in the increased vertical spacing in one or more of the increased height return bends of the serpentine coils of the indirect heat exchange section. Heat in the evaporative liquid is passed to air which is drawn generally passing downwardly or upwardly through the indirect heat exchange section and outwardly from the closed circuit fluid cooler or heat exchanger assembly by an air moving system such as a fan. The evaporative liquid draining from the indirect or direct heat exchange section is typically collected in a sump and then pumped upwardly for redistribution across the indirect or direct evaporative heat exchange section.
The type of fan system whether induced or forced draft, belt drive, gear drive or direct drive can be used with all embodiments presented. The type of fan whether axial, centrifugal or other can be used with all embodiments presented. The type of tubes, material of tubes, tube diameters, tube shape, whether finned or un-finned, the number of tube passes, number of return bends, number of increased vertical spaces, can be used with all embodiments presented. Further, the coil may consist of tubes or may be a plate fin type or may be any type of plates in any material which can be used with all embodiments presented within. The type of fill, whether efficient counterflow fill, contaminated water application fills or any material fill can be used with all embodiments presented.
Accordingly, it is an object of the present invention to provide an improved heat exchange apparatus, which could be a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, which includes an indirect heat exchange section with increased spacing formed in one or more return bends of the serpentine tube forming the indirect heat exchange section.
It is another object of the present invention to provide an improved heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, including an indirect heat exchange section that comprises a series of serpentine tube runs with increased vertical spacing between one or more of the tube runs and with a direct heat exchange located in one or more of the areas of increased vertical spacing.
It is another object of the invention to provide an improved heat exchange apparatus comprising an indirect heat exchange section comprised of serpentine coils with both a primary evaporative liquid distribution system at or near the top of the serpentine coils and a secondary evaporative liquid distribution system located below the top of the serpentine coils. Further the primary and secondary evaporative liquid distribution systems may be selectively operated such that water may be preserved.
It is another object of the present invention to provide an improved evaporative heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, including at least two indirect heat exchange sections that comprise a series of serpentine tube runs with increased vertical spacing between one or more tube runs and with a direct heat exchange located in one or more of the areas of increased vertical spacing between tube runs.
It is another object of the present invention to provide an improved evaporative heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, including at least two indirect heat exchange sections separated by an increased vertical spacing with an optional direct heat exchange located in the increased vertical space between indirect heat exchange sections.
It is another object of the present invention to provide an improved evaporative heat exchange apparatus such as a closed circuit fluid cooler, fluid heater, condenser, evaporator, air cooler or air heater, where direct heat exchange sections located in one or more of the areas of increased vertical spacing between tube runs or alternatively located between increased vertical space between indirect heat exchange sections are easily accessible and replaceable for serviceability.